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Evidencia sísmica de un desprendimiento de la corteza inferior debajo de la bahía de San Francisco, California
Science (New York, N.Y.)
|September 2, 1994
Resumen
El Experimento de Imágenes Sísmicas del Área de la Bahía de San Francisco (BASIX) encontró un reflector importante a 15 km de profundidad. Este reflector sísmico probablemente marca un desprendimiento inferior de la corteza, potencialmente un segmento del límite de la placa.
Área de la Ciencia:
- La geofísica es la geofísica.
- Sismología Sismología Sismología.
- Geología Estructural Geología estructural.
Sus antecedentes:
- El Área de la Bahía de San Francisco es tectónicamente compleja, situada en el límite entre las placas de América del Norte y el Pacífico.
- Modelos termo-mecánicos y geológicos anteriores han propuesto la existencia de una superficie de desprendimiento inferior de la corteza.
- Comprender la estructura del subsuelo es crucial para la evaluación del peligro sísmico y la dinámica de los límites de las placas.
Objetivo del estudio:
- Para investigar la estructura subterránea profunda debajo de las bahías de San Francisco y San Pablo utilizando imágenes sísmicas.
- Para identificar y caracterizar reflectores prominentes dentro de la corteza inferior.
- Evaluar la importancia potencial de los reflectores observados en el contexto de los modelos de límites de placas.
Principales métodos:
- Adquisición y análisis de datos de reflexión sísmica del Experimento de imágenes sísmicas del Área de la Bahía de San Francisco (BASIX).
- Análisis de velocidad para determinar la profundidad y las propiedades de las capas subterráneas.
- Interpretación de datos sísmicos para identificar las principales interfaces y estructuras geológicas.
Principales resultados:
- Identificación de un prominente reflector de la corteza inferior a aproximadamente 15 km de profundidad por debajo del área de estudio.
- Los análisis de velocidad indican que este reflector separa las rocas de ensamblaje franciscano de una corteza inferior máfica.
- El reflector exhibe características consistentes con un contraste reológico y de composición significativo.
Conclusiones:
- El reflector de la corteza inferior identificado probablemente representa una superficie de desprendimiento.
- Esta superficie de desprendimiento puede corresponder a un segmento subhorizontal del límite de la placa de América del Norte y el Pacífico.
- Los hallazgos apoyan y refinan los modelos termo-mecánicos y geológicos existentes del límite de la placa de la región.
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